In semiconductor industry, integrated circuit (IC) products can be categorized into three types: logic circuits, memory and analog circuits. The memory devices account for a relative large portion in the IC products. With the continuous development of semiconductor technologies, to broaden the applications of the memory devices, there is a need to form the memory devices and other devices in a same chip simultaneously so as to form an embedded semiconductor memory apparatus. For example, if the memory devices are embedded into a central processing unit (CPU), the memory devices need to be compatible with the CPU platform having the embedded memory devices; and the size and the corresponding electrical properties of the memory devices are retained.
Usually, the memory devices need to be compatible with the embedded logic apparatus. An embedded semiconductor device often have a logic region and a memory region. The logic region includes logic devices; and the memory region includes memory devices. With the continuous development of the memory technologies, a few types of semiconductor memory devices have been developed, such as static random access memory (SRAM), dynamic random access memory (DRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM) and Flash memory. Because SRAM has the characteristics including low power-consumption and high working speed, SRAM and its fabrication methods have attracted more and more attentions.
However, it is desirable to enhance the performance of the SRAM in the semiconductor device so as to improve the overall performance of the semiconductor device. The disclosed methods and semiconductor structures are directed to solve one or more problems set forth above and other problems in the art.